Methods and apparatus for lining pipes are currently available.
One proposal to line existing pipelines is disclosed in U.S. Pat. No. 4,687,677 (Jonasson). The proposal involves introduction of a flexible hose-shaped liner containing a curable plastic material into the pipeline to be lined. The flexible liner is introduced into the pipeline in an uncured state and is pressed out against the inside of the pipeline by means of compressed air. The flexible liner is then hardened in place by exposing the curable thermoset resin material to radiation energy. A somewhat similar proposal is disclosed in WO 92/16784 (Lundmark). In this latter proposal, the hose-shaped liner is introduced into the pipeline by either drawing in the liner or by everting the liner into the pipeline.
There have been various proposals for lining conduits involving installation of a liner as a tube which is everted into the passageway being lined, and which comprises an inner layer of resin absorbent material surrounded by a membrane. As the tube is everted, uncured resin is applied to the everting face of the tube to impregnate the layer of resin absorbent material which is then presented to the surface of the passageway. The everted tube is held in place by fluid pressure until the resin cures to form a rigid lining on the passageway surface. One such proposal is described in GB 1512035.
With lining proposals involving eversion of a tube comprising a layer of resin absorbent material, it is most important for there to be effective impregnation of the resin absorbent material. EP 0 082 212 attempts to address this need by provision of a vacuum inside the tube in order to remove air from the resin absorbent material at the everting face so that such material is in an optimum condition to receive the resin presented to it, thereby ensuring effective penetration of the resin into the absorbent material. However, the method outlined of providing the application of vacuum to the tube is a cumbersome procedure, involving positioning of a vacuum pipe within the tube when it is in a collapsed condition prior to eversion.
Additionally, the resin is presented to the everting face of the tube in the form of a large plug of uncured resin in the passageway to which back pressure is applied. This is employed to support the plug of resin and drive the plug, and the seal within the pipe, forward. Consequently, it is necessary for the everting tube to push the plug of uncured resin along the passageway, with the result that the plug of uncured resin can be under high and variable pressure. The fact that the plug of resin is under high variable and uncontrolled pressure can cause difficulties, one being that ongoing delivery of replenishment resin to the plug can be complicated. Further, as there is no monitoring present, there is no knowledge of the size or consistency of the volume of resin. In particular, there is no feed back to determine if the volume trapped between the everting tube and the seal is air or resin. Also, with an uncontrolled resin “plug”, the air that becomes trapped in the resin volume cannot escape.
It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country.